Number of actively running replications.
This value represents the threshold to trigger the automatic replication
scheduler.
The system will check every interval milliseconds how many replication
jobs are running, and if there are more than max_jobs active jobs,
the scheduler will pause-and-restart up to max_churn jobs in the
scheduler queue.
Making this value too high could cause performance issues, while making
it too low could mean replications jobs might not have enough time to make
progress before getting unscheduled again.
This parameter can be adjusted at runtime and will take effect during next
rescheduling cycle:

Maximum number of replication jobs to start and stop during rescheduling.
This parameter, along with interval, defines the rate of job replacement.
During startup, however, a much larger number of jobs could be started
(up to max_jobs) in a short period of time:

HTTP connection timeout per replication.
This is divided by three (3) when the replicator makes changes feed requests.
Even for very fast/reliable networks it might need to be increased if
a remote database is too busy:

If a request fails, the replicator will retry it up to N times. The
default value for N is 5 (before version 2.1.1 it was 10). The requests
are retried with a doubling exponential backoff starting at 0.25
seconds. So by default requests would be retried in 0.25, 0.5, 1, 2, 4
second intervals. When number of retires is exhausted, the whole
replication job is stopped and will retry again later:

List of replicator client authentication plugins. Plugins will
be tried in order and the first to initialize successfully will
be used. By default there are two plugins available:
couch_replicator_auth_session implementing session (cookie)
authentication, and couch_replicator_auth_noop implementing basic
authentication. For backwards compatibility, the no-op plugin should be used at
the end of the plugin list: